Improvement in mfting-jack



I To ALL WHOMI'T MAY OONOERN:

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Letters .Patent No. 78,167, dated May 19, 1868.

IMPROVEMENT -IN LI'rIIIiIc-IEOIL` ilgeidgthule ritmes tu it 113m mitmmet uns matting um nf the same.

Be it known that I, JAMES WILKINSON, of Bowling Green, in the county ofPike, and State of Missouri, have made certain new andy usefulImprovements in Lifting-Jacks and I do hereby declare that the followingis a full and clear description thereof, reference being had to theaccompanying drawings, and to the yletters of reference marked thereon.

This invention relates to a. 1ifting-jack wherein a movable fulcrum isactuated by the lever that raises the` weight in a vertical direction ateach successive stroke of the said lever, in such a manner as tomaintainI the fulcrum at a uniform distance from the weight to heraised;

l v To enable those skilled in the art to make and use my improved jack,I will proceed to describe its construction and operation.

Figure 1 of the drawings is a front elevation of the improved jack. lFigure 2 is a transverse sectional elevation of the same.

Figure 3 is an inside elevation of one of the fulcrum-posts, and showingsections of'the fulcrum-pins in their sockets.

The fulcrum-posts A'are to be erected upon a platform, A1, and havetheir top ends connected together by4 a cap-piece, A2., Grooves a a a3a4 are to be made in the' inside faces of the posts A, for the receptionof the fulcrum-pins 6. The grooves a? a3 are formed in aregularsuccession of segmental curves, and have steps at the points x ze, atthe intersection of two curves. These steps cause lthe'bottoms of thesaid grooves al a3 to present a serrated section in elevation'.V Thesteps m a; are cut squarely into the post in such a mannonas to allowthe pins b to rest upon them, and above each step the bottoms of thesaid grooves'arebevelled forward sucently far to form the next stepabove. Between the points :c a: the grooves al as are segments ofcircles, the segments in a1 being described from the points x in a.3 ascentres, and the points :c in a in turn servingfor centres from which todescribe the segments of a3.

The `double fulcrum-head `B has four bearing-pins, b, which fitin thegrooves a a in such a, manner as to 'rest on the steps :cof saidgrooves, as shown .best in g. 3. These pins 'are arranged to slide intocavities in the head B, as shown by thebroken-out `section in' iig. 1,which also'discloses springs behind the said pins, that force the pinsforward into the grooves, but yield sudiciently to allow the pins to.retreat into the head, when moving up the incline between the steps, asis also shown in fig. 1. vA lever, C, is 'inserted into the'hedB, and asits outer end is worked alternately up and down, first one side of thefulcrnm-head, .and then the other, is raised so as to' allow the pins bto rest on the steps x, and in this manner both the lever and itsfulcrum are raised with the weight, which may be placed on -top of thep-rop D, or attached to the hook When'thefulcrumblock shall inthis-manner have been raised to the top of the grooves al a", the pins bwill be pushed forward into the grooves a2 a, in which they will 4thenslide down to the bottoms of the said grooves, and thence again I, intoal er1-where theraising operation may be repeated.

Having described my invention, what I claim, is y 1. The posts A A, whenprovided with the segmental serrated grooves al a3, and combined with amovable fulcrum, B, substantially in the manner and for the purposeherein shown and described.

2. I claim the fulcrnm-head B, whenY provided with the spring-bearingpinsb, and otherwise arranged, as'

herein set forth and described.

In testimony of which invention, I hereunto sct my hand, in presence ofJAMES WILKINSON. Witnesses:

M. RANnoLrI'I, GEO. W. Hnannr.

